In this paper, we propose a dynamic lightpath conguration method for WDM ring network. With this method, lightpaths are established according to the congestion state of node and are released after some holding time. The performance of the proposed method is evaluated in light and heavy traffic cases. In the light traffic case, a single node in WDM ring network is modeled as a multiple queueing system, while M/G/1/K and M/G/c/c queues are used for the heavy traffic case. In both cases, loss probability of packet flow and wavelength utilization factor are derived. We also explore the performance of our proposed method by simulation. Numerical examples show that our analytical models in both cases are useful to predict loss probability of packet flow and wavelength utilization factor. Moreover, in the light traffic case, it is shown that small holding time is effective even when lightpath establishment/release time is small.